Tarquinius Superbus

Kill your wife and become king
Lucius Tarquinius Superbus (the proud) was the seventh and last of the
Roman kings.
Tarquinius story starts with him murdering his first wife Tullia.
Simultaneously her sister (also named Tullia) murdered her husband (his
brother). Apparently unsuspected, these two then got married. Over the
years
Tullia talked into her husband that his throne had been stolen by her
father Servius
Tullius.
After Tullius had reigned for 44 years , he was murdered by Tarquinius
and Tullia drove her chariot over her fathers dead body that was lying
in the street.

A tyrant
Tarquinius Superbus seized the power by force, had his opponents in the
senate murdered and reigned like a tyrant.

Sub doing of Gabii
His son Sextus Tarquinius first helped him in conquering Gabii by
betrayal. He made the Gabians believe he had fled from his tyrannical
father, won their trust and after some time had his opponents in Gabii
executed. Then without a battle Gabii fell in Roman hands.
Lucius built the temple of Jupiter that his father
had promised on the Capitoline hill.

Sibylline books
Tarquinius Superbus bought the books from the Sibylle
of Cumae. He claimed that she offered
him 9 books for an exorbitant
high price. When he tried to negotiate about that price, Sibylle tossed
three of the books into the fire.
For the six remaining books she asked the same price as she had
asked for the nine books. When Tarquinius made a remark about this,
again she threw three of the books into the fire.
And again she asked the same price. Fearing to have to leave empty
handed, Tarquinius accepted and paid the price for three where he could
have had nine books.
More likely is that Tarquinius invented this story to defend himself
why he had paid too much for the three books.
The books were kept in a room beneath the temple of Jupiter on the Capitoline hill.
In times of great dangers these books were consulted
by the decemviri (ten-men) in order to find out which religious
measures had to be taken that would appease the gods.

Rape of Lucretia
Sextus fell in love with Lucretia, Collatinus' wife. He
showed
this love by raping her. The next day she sent for her
father and husband each together with an entrusted friend. As soon
as Spurius Lucretius with Publius
Valerius and L. Tarquinius Collatinus with Lucius Junius Brutus had arrived she told them what had happened and
made them swear to revenge her. After they did so she
killed herself with a knife.
The men decided to expel the royal family.
Tarquinius at that moment was waging a war and when he returned he
found the gates of Rome closed.